1. Field of the Invention
The prompt detection of forest and surface fires is crucial for successfully fighting them. To this day, fire watches requiring the deployment of substantial numbers of personnel are set up in many territories at times when fires are likely to erupt, involving the visual observation of the territory from elevated vantage points or dedicated towers.
2. Description of Background Art
The detection of fires and/or smoke in outdoor areas by technical means has developed to some sophistication and a variety of options.
Earlier systems mostly evaluate the IR spectrum, mainly using sensor cells. For reasons of cost, IR cameras are used less frequently. A typical representative is the system described in [1] (U.S. Pat. No. 5,218,345), which uses a vertical array or line of IR detectors. This detector array is positioned in front of a reflector for horizontal swivelling together with it so as to scan a territory. The sensitivity of the sensors within the array is graded to prevent an over-emphasis of the foreground relative to the near-horizon areas.
[2] (DE 198 40 873) describes a process which uses different types of cameras and evaluates the visible spectrum. The parallel application of several different methods of analysis makes possible the detection of both fire and smoke. An essential feature is the comparison of reference images in memory with current images by way of generating differential images and by the application of analysis algorithms to the latter, with evaluation focused on texture properties, above all.
For detection, the system described in [3] (U.S. Pat. No. 5,289,275) evaluates relative colour intensities in the visible spectrum in addition to the TIR range (thermal infrared range), based on the assumption that, in particular, the Y/R (yellow to red) and B/R (blue to red) ratios contain features significant for fire detection.
The systems described in [4] (U.S. Pat. No. 4,775,853) and [5] (U.S. Pat. No. 5,153,722) evaluate the IR, UV and visible ranges of the spectrum in combination, assuming in particular that a significant ratio of the IR and UV intensities is indicative of fire.
These and various other publications not mentioned above are concerned exclusively with means and methods for the direct outdoor fire and/or smoke detection, i.e. under open-country conditions and over great distances. Procedures involving a complex monitoring of territories are not taken into consideration. Methods of this type must include at least one of the aforesaid processes for automatic fire and/or smoke detection and, in addition, must be designed to co-operate with further automatic or personnel-operated processes up to and including the issuing of instructions to firefighting crews.